The present invention relates generally to Directory Number portability in telecommunication systems, and more particularly to allowing a subscriber to keep a single Directory Number when relocating to a different access point among one or more interconnected telecommunication systems.
It is customary for the telecommunication industry to use acronyms when referring to established components and services. The ones that are used in this disclosure are listed as follow:
A Directory Number (DN) in traditional telephone systems is used to ring a telephone on a given line of a given local telephone exchange. A local exchange may be one of many interconnecting exchanges that constitute what is known as the Public Switched Telephone Network (PSTN). Each exchange, also referred to as a switch in PSTN, is provisioned with a plurality of access points or telephone lines, each addressable by a 4-digit extension [YYYY]. Subscribers may call each other on the PSTN by dialing each others Directory Number. In North America the DN is a 10 digit number and until recently it also represents the address of the exchange provisioning the DN. Each exchange is identified by a 6-digit exchange code [NPA-NXX] and the DN has been formed by concatenating the exchange code with the exchange extension in the format [NPA-NXX]-[YYYY].
The Directory Number (DN) then has been serving a dual function, namely as an address for an exchange and its extension, and also as a subscriber ID (identity) number by which the subscriber could be reached. It works well if the subscriber is fixed at the originally assigned access point or line. The problem arises when the subscriber moves to another access point. If the new access point is still served by the same exchange, the subscriber is usually allowed to keep the same number since the exchange could be reconfigured to provision the same extension number at the new access point. However, when the new access point is served by a different exchange, the subscriber can no longer retain the existing DN since the new exchange will have an exchange code different from that encoded in the original DN. The subscriber will have to be given a new DN appropriate for the new exchange. In either case, every time a subscriber makes a move, it may be days or weeks before the new service is in place.
Even if the subscriber has not moved outside the service area of an existing exchange, the subscriber may wish to switch to a more competitive service provider or to subscribe to other types of telecommunication services such as wireless, or internet or cable telephony.
From the foregoing description, it can be seen that there are three general types of number portability arising from moving from one access point to another. The first is Service Provider Portability which allows a subscriber to change access/service provider without changing the DN. The second is Location Portability which allows a subscriber to change physical locations without changing the Directory Number. The third is Service Portability which allows a subscriber to change service (e.g., POTS to ISDN) without changing the DN. In all cases, whenever the subscriber moves to a different exchange, the existing DN is no longer compatible with the address of the new exchange.
The lack of number portability is inconvenient for today""s subscribers who tend to be more mobile and use a variety of telecommunication services. Furthermore, this impedes deregulation in the telecommunication industry, as it gives the incumbent service provider unfair advantage over a competing service provider. This is because a subscriber may be reluctant to change service provider if it also means a change of Directory Number.
Call forwarding is one prior art solution to location number portability. Call forwarding basically engages two directory numbers on two lines and redirects a first Directory Number to a second Directory Number. Depending on the capability of the switched network, there are two ways of implementing call forwarding. One is to encode the second Directory Number directly into the exchange switch. The other, when the switch is part of an IN/AIN switched network, is to trigger the switch on the DN to lookup second Directory Number from a network database.
FIG. 1A illustrates a conventional call forwarding scheme by encoding the call forwarding information into the exchange switch. A subscriber has a Directory Number DN1 on a telephone line L1 provisioned on an exchange X1. The subscriber is able to forward calls for DN1 to DN2, where DN2 is on a telephone line L2 provisioned on an exchange 2. The exchange X1 is programmed to respond to call-forwarding requests by the subscriber. In step (0), the subscriber can dial a special call-forwarding setup code on L1 and input into X1 the forwarding number DN2. The exchange X1 encodes this information in its Routing Table (RT) so that if a call to DN1 is received, it is rerouted to DN2 on X2 accordingly.
FIG. 1A shows a network of exchanges X0, X1 and X2 interconnected by voice trunks. Typically, when a call connection is to be made, a call stream is established serially from one exchange to another forming a series of circuits until the destination exchange is reached. Given the DN, each exchange has a RT that indicates which is the next exchange in the stream to establish the link. In order to setup the linkage (call setup) efficiently, the status and control signals associated with a call are carried in a digital network using a Signaling System 7 (SS7) protocol on it own network. The signaling is in the form of a digital packet know as Initial Address Message (IAM). The IAM packet is routed between exchanges or other points of the digital network by a Signal Transfer Point (STP) which is essentially a digital packet router. In the example shown, a call to DN1 originates from a line L0 of the exchange X0. The exchange X0 determines from its RT that DN1 resides in an exchange X1 and proceeds to set up the call. The call setup involves, in step (1), forming an IAM0(DN1) packet to be routed from X0 to X1 by the STP, and with which the a circuit between X0 and X1 is made available. At X1, its RT indicates that DN1 is forwarded to DN2 at X2. Then in step (2) an IAM1(DN2) packet reflecting the redirection is routed form X1 to the exchange X2 that is provisioning DN2 to set up the next leg of the circuit. In this way, a call made to DN1 is forwarded to connect at DN2.
The switch-based call-forwarding scheme has several disadvantages. Two Directory Numbers, DN1 and DN2, are engaged and therefore the solution is uneconomical. Furthermore, this two-number solution is not symmetric in that when dialing out from the forwarded-to line L2, the line is still identified with DN2. To set up the call-forwarding service, the subscriber must initiate it from the original access point L1. Also, the call routing is not efficient, as all calls for DN1 must first visit the original exchange X1 before being rerouted to X2.
FIG. 1B illustrates another conventional call forwarding scheme as implemented by an Intelligent Network or Advanced Intelligent Network (IN/AIN). In this type of intelligent network, the interconnecting switches X1, X2, . . . cooperate with one or more programmable switch (PX) also known as Intelligent Peripheral (IP) and a database server known as Service Control Point (SCP).
In step (0), to activate the call-forwarding feature, a subscriber typically dials an 800 number which connects the subscriber to an IP. After authentication, the subscriber can input the original DN1 and the new DN2 number. The IP interacts with SCP to have the forwarding of DN1 to DN2 entered into the SCP. It then interacts with the switch X1 to have the call-termination trigger set on the switch to trigger on the call-forwarded number DN1. Subsequently, when a call to DN1 is received in X1, it will trigger X1 to obtain the call-forwarding information directing to DN2 by performing a lookup on the SCP. The switch X1 then uses the retrieved information to route the call to X2, L2.
In the example shown in FIG. 1B, a call to DN1 originates from a line L0 of the exchange X0. The exchange X0 determines from its Line Translation Table (LTT) that DN1 resides in an exchange X1 and proceeds to set up the call. The call set up involves, in step (1), forming an IAM0(DN1) packet to be routed by the STP to X1, by which the a voice circuit between X0 and X1 is made available. In step (2), at X1, the call to DN1 triggers a query through the STP to lookup forwarding information from the SCP. In step (3) the SCP returns the call forwarding information about DN2. In step (4) X1 uses the DN2 information to form its IAM1(DN2) packet. Then in step (5) the IAM1(DN2) packet is routed form X1 to the exchange X2 that is provisioning DN2 to set up the next leg of the voice circuit. In this way, a call made to DN1 is forwarded to connect at DN2.
The intelligent network-based call-forwarding scheme improves on the switch-based scheme in that the call-forwarding information is not hard-coded into the exchange but rather retrievable from a more flexible database. The service need not be set up at the original access point L1 but could be set up by the subscriber from any access point including L2 that has access to the IP. Otherwise, it still has the same disadvantages as that of switch-based scheme.
Another prior art solution to number portability is directed to Service Provider Portability which is a result of recent government mandates in the United States of America. There has been legislation to deregulate the telecommunication industry, primarily to transform a monopolistic industry controlled by a handful of tightly regulated incumbent telephone companies to a plurality of competing telecommunication companies operating in a free market setting. To this end, any conditions that accord unfair advantages to the incumbent companies must be dismantled. As mentioned before, user inertia owing to the lack of number portability among service providers is one such concern. This concern has been addressed in the United States Communications Act of 1996. The 1996 Act defines (Service Provider) xe2x80x9cnumber portabilityxe2x80x9d as xe2x80x9cthe ability of users of telecommunications services to retain, at the same location, existing telecommunications numbers without impairment of quality, reliability or convenience when switching from one telecommunications carrier to another.xe2x80x9d Overseeing compliance of the 1996 Act, the United States Federal Communications Commission (FCC) has ordered telephone companies to implement Service Provider Portability according to the Local Routing Number (LRN) method. The LRN method is specified in a series of publications, the latest of which is xe2x80x9cGeneric Switching and Signaling Requirements, Issue 1.05, Aug. 1, 1997, editor: J. J. Lichter, Lucent Technologies.
The essence of LRN method is to decouple the subscriber""s ID function from the exchange address function of the Directory Number (DN). The DN will be considered primarily as an ID number for a given subscriber. The exchange that has ported numbers will have an address independently and uniquely given by the Local Routing Number (LRN) which is a 10-digit number. If the DN is not ported from its originating exchange, then the exchange""s LRN can still be obtained from the DN. On the other hand, if the DN is ported to a second exchange, then the second exchange must be addressed by its own LRN which is different from that obtained from the DN.
FIG. 2A illustrates the LRN scheme for implementing Service Provider Portability as required by the United States Local Number Portability (LNP) authorities. The LNP scheme is designed for DN portability from one service provider to another servicing the same locality or Local Access Transport Area (LATA). Initially, it will offer DN portability between an Incumbent Local Exchange Carrier (ILEC), shown as Service Provider N, and a Competitive Local Exchange Carrier (CLEC), shown as Service Provider 2. Basically, it employs the dynamic lookup capability of an IN/AIN switched network In addition to the SCP database, each service provider is provisioned with an additional LNP-SCP database for storing the routing information for a ported subscriber. In particular, the routing information will contain the LRN of an exchange that a given DN has ported to. When a call to a DN that has been predefined as LNP portable, the Service Control Point""s (SCP) service logic programmed in the exchange will initiate an AIN or IN based LNP query to the LNP-SCP to obtain the LRN for the destination exchange to which the DN that has been ported. The queried LRN is then returned to the exchange to route the call accordingly.
In the example shown, a subscriber was given DN1 when originally subscribed to a line L1 provisioned by an exchange X1 of Service Provider N. When the subscriber subsequently changes to Service Provider 2, DN1 has been ported to a line L2 on an exchange X2. In step (0) the change in service provider is submitted by both Service Provider N and Service Provider 2 to an inter-service provider mediation service who oversees the incorporation of the porting information into the LNP-SCP databases of the various service providers. Thus, over a period of days or weeks, the porting information, DN1 together with the address of X2 (i.e. LRN(X2))) are entered into the respective LNP-SCP of Service Provider N, Service Provider 2 and Service Provider Nxe2x88x921 as shown in FIG. 2.
In addition to mediation and storing of LRNs in the LNP-SCP database of the various service providers, the LNP implementation also mandates the exchanges to be xe2x80x9cLNP-enabledxe2x80x9d, i.e. upgraded to be able to handle the LRN scheme.
At some point, a connecting exchange must look up the ported information from one of the LNP-SCPs in order to complete the circuit to the ported location. Part of the LNP scheme is to minimize the burden imposed on the service provider being ported from (Service Provider N) for doing the lookup, but to let the service provider adjacent to it (Service Provider Nxe2x88x921) to perform the lookup and routing. Thus, when a call is made to DN1, it is typically routed to Service Provider Nxe2x88x921 before attempting to do a lookup.
In the example shown in FIG. 2, a call to DN1 is made from a line L0 in one of the exchanges X0 of Service Provider Nxe2x88x921. In step (1), the LNP-enabled exchange triggers on DN1 to do a query for LRN. In step (2), this induces a STP to lookup LRN(DN1) from LNP-SCP. In step (3), the address of the destination exchange, X2=LRN(DN1), is returned to X0. In step (4), a call setup is initiated from X0 to an Access Tandem exchange (AT). The LAM0(DN1, LRN(DN1)) being routed from X0 to AT now has the LRN of X2. In step (5), the AT set ups the next leg of the connection and connects into the domain of the Service Provider 2 containing the destination exchange X2. In steps (6) and (7), through call setups, the connection is made all the way to the destination exchange X2 where the call is connected to a designated line L2.
Since only one LNP-SCP lookup need be made to obtain the porting information, the exchanges are designed to sense whether a lookup has been made or not. This is accomplished in the LRN method by setting a flag in the IAM signaling packet that is passed from exchange to exchange. The LRN method specifies that the nth bit of the Forward Call Indicator (FCI) field of the IAM is to be used for this purpose (See FIG. 5(a)). If an LNP-SCP lookup has not been made, the exchange responsive to that condition will initiate a lookup, otherwise no lookup will be made.
FIG. 5(c) shows the IAM field values after a LNP query. This applies to the case in which a DN1 originated from an exchange X1 is ported to an exchange X2 with an address LRN2 using the LRN method. In the LRN method, the address of the destination exchange is obtained from the CDPN field. Thus, it is the field in which the Local Routing Number (LRN) is entered. After an LNP query, the address of the destination exchange LRN2 is returned and placed in the CDPN field. Under the LRN method, the GAP field is used to store the directory number DN1. Also, after an LNP query has been performed, the nth bit of the FCI field is set to xe2x80x9c1xe2x80x9dto prevent subsequent exchanges from repeating the query.
U.S. Pat. No. 5,758,281 issued May 26, 1998 to Emery et al. discloses a system for allowing a user to send and receive calls from a single portable handset using a single assigned number whether at home or roaming.
The following publications discloses Advance Intelligent Network (AN) and their exchanges, SS7, STP and the LNP scheme, relevant portions of them are incorporated herein by reference.
xe2x80x9cThe Intelligent Network Standards: their application of servicesxe2x80x9d, Faynberg, I., et al, McGraw-Fill, 1997
xe2x80x9cMobile and Wireless Networksxe2x80x9d, Black, Uyless. Prentice Hall, 1996.
xe2x80x9cBellCore specification of SS7xe2x80x9d, GR-246-CORE, Decmber. 1995, BellCore.
xe2x80x9cCommon Channel Signaling Network Interface Specificationxe2x80x9d, GR-905-CORE, March 1995, BellCore.
xe2x80x9cITU-TS specifications of signaling system Number 7xe2x80x9d, CCITT xe2x80x9cwhite Bookxe2x80x9d Volume VI, Fasciles VI.7, VI.9 (Q.700 Series Recommendations).
xe2x80x9cAIN 0.1 Switching Requirementsxe2x80x9d, TR-NWT-001284, BellCore
xe2x80x9cAIN 0.2 Switch-Intelligent Peripheral Interface Generic Requirementsxe2x80x9d, GR-1129-CORE, BellCore
xe2x80x9cAIN Switch-Service Control point/ Adjunct Interface Generic Requirementsxe2x80x9d, GR-1299-CORE, Decmber. 1995, BellCore
xe2x80x9cLNP capability specificationsxe2x80x9d, GR-2936-CORE Draft, May 1996, BellCore.
xe2x80x9cSTP generic Requirementsxe2x80x9d, GR-82-CORE, December. 1995, BellCore.
xe2x80x9cCompatibility Information for Interconnection of a wireless service provider and a local exchange carrier networkxe2x80x9d GR-145, May 1998, BellCore
xe2x80x9cTelephone Number Portability; NANC Recommendation concerning LNP administration, wireless and wireline integrationxe2x80x9d, CC docket No. 95-116, NSD file No. L-98-84
The LRN method has been designed to narrowly address number portability between service providers serving the same locality. While the LRN method introduces the important feature of LRN addressing of the exchanges, independent of the Directory Number, there remains no universal single-number portability solution. For example, given the service provider LNP implementation, a subscriber may retain the DN when switching service provider within the same LATA, but still has problems when moved to another exchange. Similarly, the problem of having a single DN between wire-line and wireless, or between other communication systems such as internet or cable telephony, is still not addressed.
It would be desirable for the subscriber to be able to retain his or her Directory Number when accessing from different access points of a plurality of interconnected communication systems.
Accordingly, it is a general object of the present invention to provide a system and method for number portability from one access point to another among one or more interconnected telecommunication systems.
It is an object of the present invention to provide a system and method for One-Number-Service (ONS) which enables a subscriber""s directory number to be easily ported from one access point to another among one or more interconnected telecommunication systems.
It is an object of the present invention to provide a system and method for One-Number-Service (ONS) which enables a subscriber""s directory number to be easily ported from one access point to another among a Local Access Transport Area (LATA).
It is an object of the present invention to provide a system and method for One-Number-Service (ONS) which enables a subscriber""s directory number to be easily ported from one service provider to another service provider.
It is an object of the present invention to provide a system and method for One-Number-Service (ONS) which enables a subscriber""s directory number to be easily ported between different telecommunication services.
It is an object of the present invention to provide a cost effective and reliable system and method for number portability from one access point to another among one or more interconnected telecommunication systems.
These and additional objects are accomplished by providing a system and method for maintaining and accessing number portability information in order to complete a call to a ported directory number to its ported location. In particular these objects are accomplished by enhancing existing telecommunication systems in a cost effective manner, with minimum modification.
According to one aspect of the invention, in an intelligent (IN/AIN) telecommunication network system, the Signal Transfer Points (STPs) are enhanced into One-Number-Service STPs or (OSTPs) to query the address of the exchange the directory number has ported to during a call setup process and to modify the call setup accordingly. In particular, the directory number contained in the signaling packet for a call setup is examined and used to look up a database containing the new address (LRN) of the exchange the directory number has ported to. The address field for the destination exchange in the signaling packet is then updated with the new address in order for the call setup to complete the call to the ported exchange.
In one embodiment, all ported numbers, whether they are LNP-ported numbers (i.e., between service providers by the LRN method) or ONS-ported numbers (i.e., between two access points in general) are processed by OSTP query during call setup.
In another embodiment, where the telecommunication network system supports Service Provider portability or MNP), directory numbers that are LNP-ported are handled by the LNP scheme which requires an LNP-enabled exchange to perform a query by means of a Transaction Capable Application Part (TCAP) signaling via a STP to a database containing the new address (LRN) of the exchange the directory number has ported to. One-Number-Service (ONS) portability is accomplished by using the LNP scheme to handle the LNP-ported numbers and the OSTP query during call setup for other non LNP-ported directory numbers or for LNP directory numbers that have been ported more than once.
The conventional LRN method is very expensive as it involves costly modification to all the exchanges. In any case, it still does not address other number portability outside that of service providersxe2x80x2. The ONS scheme provided by OSTP query during call setup is advantageous because unlike the LRN method the plurality of interconnecting exchanges need not be modified, instead, only the relatively fewer STPs need be enhanced to become OSTPs.
According to another aspect of the invention, where the telecommunication network system supports Service Provider portability or (LNP), directory numbers that are LNP-ported are handled by the LNP scheme which requires an LNP-enabled exchange to perform a query by means of a TCAP signaling via a STP to a database containing the new address (LRN) of the exchange the directory number has ported to. When One-Number-Service (ONS) portability is applied within a service provider""s domain, it is accomplished by an enhanced STP with TCAP processing that responsive to an ONS-ported number, queries a database containing ONS porting information.
According to yet another aspect of the invention, the exchanges among the telecommunication network system are enhanced to query a database containing LNP porting information in response to an LNP-ported directory number, and to query a database containing ONS porting information in response to an ONS-ported directory number.
Additional objects, features and advantages of the present invention will be understood from the following description of the preferred embodiments, which description should be taken in conjunction with the accompanying drawings.